1. Field of Invention.
This invention relates to the field of electronic circuitry sensing and protecting a battery charging circuit against the effects of reverse polarity and short circuiting originating at the battery.
2. Description of Prior Art.
Circuitry is known in the art as with battery chargers to protect the battery being charged from over-voltage in turning off the charging circuit when a prescribed value of battery voltage is achieved as disclosed in the U.S. Pat. No. 3,205,422 issued to C. M. Gold. The limitation in Gold is that it senses voltage in only one polarity and only in one direction, that is, from the current source only and is incapable in sensing a condition of undesirable power dissipation resulting from a reverse polarity or a short circuiting condition originating with the battery being charged.
Disclosed also in U.S. Pat. No. 3,571,608 issued to Edward T. E. Hurd, III, is a protective circuit essentially the same as that disclosed by Gold and relates only to current from the current source but does not have the capability of sensing the undesirable conditions originating with the battery being charged as above indicated.
In U.S. Pat. No. 3,668,545 to Daniel R. VonRecklinghausen, there is provided means to measure excess voltage from the input source as determined by an over-voltage protector but there is no capability here for protecting against over-voltage developing in the output current side of the circuitry. In the disclosure of this patent there is no need to protect against a current condition developing in a load as no load is contemplated here which could become a source of power. This patent provides no teaching having to do with a voltage drop caused by a condition having to do with the output of the current and originating with the load.
In the U.S. Pat. No. 3,074,006 issued to G. N. Klees, there is a disclosure having to do with the supply current to a load but there is no teaching present for protection against a problem in voltage drop originating with the load.